/*
 * Copyright (C) 2009 Leandro de Oliveira Aparecido <lehphyro@gmail.com>
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *         http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.google.code.configprocessor;

import org.codehaus.plexus.component.configurator.expression.*;

/**
 * Resolver of placeholders.
 * 
 * @author Leandro Aparecido
 * @see org.codehaus.plexus.component.configurator.expression.ExpressionEvaluator
 */
public class ExpressionResolver {

	/**
	 * True if placeholders must be replaced.
	 */
	private boolean replacePlaceholders;
	
	/**
	 * Evaluator of expressions to use.
	 */
	private ExpressionEvaluator evaluator;
	
	public ExpressionResolver(ExpressionEvaluator evaluator) {
		this(evaluator, true);
	}

	public ExpressionResolver(ExpressionEvaluator evaluator, boolean replacePlaceholders) {
		this.evaluator = evaluator;
		this.replacePlaceholders = replacePlaceholders;
	}
	
	/**
	 * Resolves the given text replacing any placeholders if necessary.
	 * 
	 * @param value Value to resolve.
	 * @return Resolved value with values replaced as necessary.
	 */
	public String resolve(String value) {
		String resolvedValue;
		
		if (replacePlaceholders) {
			try {
				Object aux = evaluator.evaluate(value);
				if (aux != null && !(aux instanceof String)) {
					throw new IllegalArgumentException("Expression [" + value + "] did not resolve to String");
				}
				resolvedValue = (String)aux;
			} catch (ExpressionEvaluationException e) {
				throw new RuntimeException("Error resolving expression [" + value + "]", e);
			}
		} else {
			resolvedValue = value;
		}
		
		return resolvedValue;
	}
	
}
